A mythology is a relatively cohesive set of myths: stories that comprise a certain religion or belief system.

Myths are generally stories based on tradition and legend designed to explain the universe, the world's creation, natural phenomenon, and anything else for which no simple explanation presents itself. Not all myths need have this explicatory purpose, however. Likewise, most myths involve a supernatural force or deity, but many are simply legends and stories passed down orally from generation to generation.

Mythology figures prominently in most religions, and most mythology is tied to at least one religion. Some use the words "myth" and "mythology" to portray the stories of one or more religion as false, or dubious at best. The term is most often used in this sense to describe religions founded by ancient societies, such as Roman mythology, Greek mythology, and Norse mythology, which were nearly extinct at one time. However, it is important to keep in mind that while some view the Norse and Celtic pantheons as mere fable, others hold them as a religion (See Neopaganism). By extension, many people do not regard the tales surrounding the origin and development of religions like Christianity, Judaism and Islam as literal accounts of events, but instead regard them as figurative representations of their belief systems.

People within most religions take offense at the characterization of their faith as a group of myths, for this is tantamount to claiming that the religion itself is a lie. However, most people concur that each religion has a body of myths that have developed in addition to scriptures.

For the purposes of this article, therefore, we use the word "mythology" to refer to stories that, while they may or may not be strictly factual, reveal fundamental truths and insights about human nature, often through the use of archetypes. Also, the stories we discuss express the viewpoints and beliefs of the country, time period, culture, and/or religion which gave birth to them.

Stories from scripture are usually not referred to as mythology except in a pejorative sense, but one can speak of a Jewish mythology, a Christian mythology, or an Islamic mythology, in which one describes the mythic elements within these faiths without speaking to the veracity of the faith's tenets or claims about its history.

Many modern day rabbis and priests within the more liberal Jewish and Christian movements, as well as most Neopagans, have no problem viewing their religious texts as containing myth; they see their sacred texts as indeed containing religious truths, divinely inspired but delivered in the language of mankind. Others, of course, disagree.

Although many people think that a mythology must be old, it does not have to be so.
Thus, for example, television and book series like Star Trek and Tarzan have strong mythological aspects that sometimes develop into deep and intricate philosophical systems.

Some critics believe that the fact that the core characters and stories of modern story cycles are not in the public domain prevents the modern story cycles from sharing several essential aspects of mythologies. Fan fiction goes some distance to relieving this problem and extending these modern mythologies.